I play on SGS, almost every night from about 21h00 to 23h00. It rocks. Sometimes, I pwn, sometimes, I suck. That's the way it goes.
I find that I can't play for too long in the evenings, however. Two hours is long enough, then I go play offline games, chat or browse the web. Unlike Counter-Strike, two hours of TF2 is a whole load of game-play. Two hours of CS is only about 15-minutes of gameplay because you spend most of your time waiting for the next round to start!
When the servers start to drop off around 22h30, the game starts to die. You need a full server for this one.
Sometimes, the game play is better than average. A few nights ago, A sniper, a HWG, a medic and myself (as a medic) completely dominated a sudden-death round. Medics can heal other medics, but not themselves. You need two medics in sudden-death. The sniper and HWG both died, eventually, leaving us two medics as the last living team members. Luckily for us, the last living team member of the other team was also a medic. The game was won with a battle of the needle guns! I normally spam rockets as a soldier but that stint as a medic stands out as the most fun I've had in an online game - EVER. (LANs not included. There's something really cool about 25 okes lanning in a double garage... with various pastry-wrapped or pizza-related sustenance and, of course, the obligatory bottles of Coke!)